If it rained 3 days out of 20 days, on what percent of days did it rain?

Number of days it rained = 3 days
Total number of days within which it rained for 3 days = 20 days.
So the percentage of days it rained = (3*100)/20
                                                         = 300/20
                                                         = 15.
So in total it rained for 15% of the days.